Self-regulating tide gate

ABSTRACT

A self-regulating tide gate system for a headwall placed over a channel, stream or river exposed to tides or floods with at least one gate opening formed therein. Disposed on the downstream side of the headwall on opposite sides of the gate opening is at least one pivotally attached door panel designed to swing downstream to allow flow in the downstream direction. When water levels are such that flow in the upstream direction is possible, the door panel is held open thereby allowing some backflow. When the backflow generates a sufficient force, the door panel closes. Attached to each door panel is a guide line. Attached to the guide lines is at least one elastic cord or strap designed to apply a variable tension force to the guide lines to hold the door panels in an open position and progressively resist closure of the door panels when the draft force generated by the upstream flow of water matches or exceeds the tension in the guide lines. The opposite end of the elastic strap may be connected to an adjustable winch that allows the operator to selectively adjust the resting length and tension exerted by the elastic strap thereby causing the gate to open earlier or later, or open and close completely or partially.

This utility patent application is based on and claims the filing date of the U.S. provisional patent application (Ser. No. 61/135,823) filed on Jul. 23, 2008.

Notice is hereby given that the following patent document contains original material which is subject to copyright protection. The copyright owner has no objection to the facsimile or digital download reproduction of all or part of the patent document, but otherwise reserves all copyrights whatsoever.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention pertains to fluid control systems, and more particularly to self-regulating tide gates (called SRT gates) used to regulate the flow of tidal water in tidelands, channels, rivers or streams.

2. Description of the Related Art

SRT gates have been used to regulate the flow of fresh, brackish, and salt water through culverts in tidally influenced areas. The water level downstream from the gate varies during the day. The diurnal tide and the river's backwater curve cause the water level to vary significantly on a daily basis.

SRT gates used in the prior art typically include a float that causes the gate to gradually close when the tide water reaches a designed elevation and open when the tide crests and there is driving head in the downstream direction. One drawback with SRT gates found in the prior art is that the float may be broken or become fouled with debris. Another drawback is that if there is insufficient flow through the gate when the tide water drops, the SRT gate doesn't open completely. On the subsequent rising tide, the upstream flow of the tide water may be choked off by the partially open gate. The diminished volume of water that fills the tidal prism upstream from the SRT gate is insufficient to push the gate open on the following falling tide and the SRT gate progressively opens less with each tidal cycle until the gate remains completely shut. As a result, the water upstream from the SRT gate does not flush in and out with the tide and becomes stagnant. Also, the migration of fish through the gate opening is precluded.

An excessive amount of tidal flushing at an SRT gate is undesirable because excessive water levels upstream can inundate developed land. In addition, brackish water saturating agricultural land can negatively impact crops that have limited tolerance for brackish water.

Because SRT gates are typically unmanned, they must automatically and reliably open completely during falling tides and automatically and reliably close at an appropriate water level during rising tides. The SRT gate must operate independently and without human intervention. Because the levels of the water may vary with different seasons, and during storm and draught conditions, the SRT gate should be easily adjustable. The SRT gate should also be easily to maintain.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved SRT gate that operates like a normal SRT gate in that it does not allow upstream flow through the SRT gate during floods, but can be selectively adjusted to allow some quantity of backflow without causing harm.

It is another object to provide such an improved SRT gate that is relatively inexpensive to install on an existing headwall with or without an existing tide gate.

These and other objects are met by a SRT gate system disclosed herein. The system includes a new or existing culvert or a barrier (hereinafter called a headwall) transversely constructed over a channel, stream or river exposed to tides or floods. Formed on the headwall is at least one square or rectangular-shaped gate opening. Attached to the headwall on a side adjacent to the gate opening is at least one pivoting door panel that swings in an upstream direction to close the gate opening or swing in a downstream direction to open the gate opening. In the first embodiment, there are two vertically aligned pivoting door panels that are attached via hinges to the headwall on opposite sides of the gate opening. In another embodiment, a single door panel is pivotally attached over the gate opening. In both embodiments, the two or single door panels automatically swing open or automatically swing shut under specific weather conditions.

Attached to each door panel or to a lever attached to the door panel's hinge is a guide line used to exert a pulling, opening force on the door panel. In the first embodiment, the guide line extends around a pulley attached to the distal end of a rigid strut. The strut extends perpendicularly from the downstream side of the headwall adjacent to the gate opening's hinge edge. Attached to the proximal end of the guide line is an elastic cord, strap, or spring which acts as a means for gradually increasing the force on the guide line when the door panel pivots into a closed position over the gate opening. In preferred embodiment, the elastic cord is a replaceable bungee cord made of polypropylene or nylon. In one embodiment, an optional tightening cable is attached to the proximal end of the bungee cord. The tightening cable is attached to a winch or some other suitable tightener that enables the operator to selectively adjust the magnitude of the pulling force exerted by the bungee cord on the guide line.

As state above, the SRT gate system may use two door panels or a single door panel over the gate opening. The guide line used with each door panel may be connected to one bungee cord so that each door panel is independently controlled. Alternatively, both guide lines may be connected to a single bungee cord used to simultaneously control both door panels so that they close and open simultaneously.

During installation, the operator selects and installs a suitable spring composed of bungee cord that will hold the door panel open when the downstream water flow exceeds the upstream tidal flow and will allow the door panel to gradually close when the upstream tidal flow increases and eventually exceeds the downstream water flow. By selecting a particular type, diameter, and length of bungee cord and by using a single strand or multiple loops of bungee cord strung between two steel rings, the operator can select the desired elastic strength. When a tightening cable and winch is used, the operator is able to manually adjust the winch to apply more or less tension force on the bungee cord so that door panel begins to close later or earlier during a rising tide. More tension causes the door panel to stay open longer against a rising tide. Less tension allows the door panel to close earlier against a rising tide. The exact tension setting of the bungee cord used depends on many factors, such as the size and length of the elastic cord, the size and shape of the door panel, and the profile and cross sections of the creek or slough upstream from the gate. The geometry of the channel upstream from the gate defines the volume of water that has to pass through the gate as the water level rises. This volume of water is related to the magnitude of the flow velocity which increases non-linearly during a rising tide or rising river stage.

The SRT gate system is easy to maintain. The only component that requires periodic replacement is the bungee cord which is simply replaced on a regular basis. By housing the bungee cord within a tube and thereby shielding it from sunlight and weather, a quality bungee cord utilizing a synthetic cover will provide multiple years of use before requiring replacement.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a headwall constructed over a creek or slough that includes one central, hydraulically controlled SRT gate and two elastic cord controlled SRT gates.

FIG. 2 is a top plan view of the headwall shown in FIG. 1.

FIGS. 3-5 are top plan views of a single SRT gate with two guide lines attached to two door panels, each connected to a guide line that connects to a single elastic cord that stretches as the gate doors are concurrently close.

FIG. 6 is a perspective view of a single door panel SRT gate mounted via hinges on a rotating tube with a lever arm attached to the upper end that connects to a guide line and elastic cord.

FIG. 7 is a partial top plan view of the single door panel SRT gate shown in FIG. 6, with the guide line being redirected over the top surface of the headwall and attached a first yoke member attached to three elastic cord segments with the opposite ends of the elastic cord segments be attached to looped to a second yoke member attached to a tension cable that is selectively adjusted in length by a winch.

FIG. 8 is a cross-sectional view of a channel with a headwall constructed thereover with a single SRT tide gate constructed therein and showing the relative position of the water at one of two possible elevations (El₁ and El₂).

FIG. 9 are two cross sectional views of the SRT gate's door panel mounted on a headwall showing the respective water levels for the downstream water on the door panel and El₁ and EL₂ as illustrated in FIG. 8.

FIG. 10 is a graph showing the predicted tidal height varying with time at a given site. For the predicted tides, water levels El₁ and El₂ occur at times T₁ and T₂.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring to the accompanying FIGS. 1-10, there is shown an improved SRT gate 10 constructed on a headwall 12 assembled transversely over a creek or slough 90 in a tidally influenced area. The headwall 12 includes at least one SRT gate 10 designed to allow upstream water 98 and downstream water 99 to pass through.

The SRT gate 10 is assembled on the downstream side of the headwall 12 on opposite sides of the gate opening 20. In the first embodiment, the SRT gate 10 includes two pivotally attached door panels 30, 36 designed to swing in the body of downstream water 99. The two panels 30, 36 are designed to automatically open and close the gate opening 20 depending on flow of water through the gate opening 20 and the elevation and volume of downstream water 99. In the first embodiment shown in FIGS. 1-5, attached to the headwall 12 and extending downstream on opposite sides of the gate opening 20 are two rigid struts 40, 45. Attached to each strut 40, 45 is a pulley 42, 47, respectively. The two struts 40, 45 are held in a perpendicularly aligned position by an optional tie line 50 that extends over the ends of the struts 40, 45 and connects at its opposite ends to the headwall 12.

Extending around each pulley 42, 47 is a guide line 52, 56, respectively. One end of the guide line 52, 56 is directly attached to one of the door panels 30, 36, respectively. The distal section of each guide line 52, 56, extends around the pulley 42, 47, respectively, while the middle section of each guide line 52, 56 extends inward towards the headwall 12 and around a second pulley 43, 48, respectively mounted on the top surface 14 of the headwall 12. Each guide line 52, 56 then extends longitudinally over the top surface 14 and converge with the other guide line and connects to a single elastic cord 60. In the first embodiment, the proximal end of the elastic cord 60 attaches to tightening cable 65 that attaches to an optional winch 70 that allows the operator to selectively adjust the tension exerted by the elastic cord 60 on the two guide lines 52, 56.

FIG. 6 is a perspective view of a second embodiment of the SRT gate 100 that uses a single door panel 30 mounted on the side of a gate opening 20. The SRT gate 100 includes a which a plurality of brackets 102 are securely mounted on the vertically aligned, rotating tube 110 supported at its opposite ends by two rigid brackets 112, 114 perpendicularly aligned and mounted on the downstream side of the headwall 12. The bracket 102 is vertically stacked on the downstream side of the door panel 30. The tube 110 is able to be freely rotated between the two bracket 112, 114. Attached to the top end of the tube 110 is a lever 115 that connects to the end of guide line 52. When the guide line 52 is aligned over the top surface of the headwall 12 and pulls on the lever 115, thereby causing the tube 110 to rotate and open the door panel 32. The proximal end of the guide line 52 is attached to the elastic cord 60. The elastic cord 60 may be attached to the top surface of the headwall 12 or attached to a tightening cable 65 that is selective wound and unwound on a winch 70.

FIG. 7 is a partial top plan view of a single door panel embodiment similar to the SRT gate 100 shown in FIG. 6, that uses a multiple elastic cord assembly 120 in place of a single elastic cord 60 or three separate elastic cords (not shown) The multiple elastic cord assembly 120 is made up of parallel elastic cord segments 130, 132, 134 attached or looped around a first yoke member 140. The first yoke member 140 is attached to the proximal end of a guide line 50. The opposite ends of the elastic cord segments 130, 132, 143 are attached or looped around a second yoke member 150 that is attached to the end of a tightening cable 65 attached to a winch 70.

In all three embodiments, the single elastic cord or the multiple elastic cord assembly 120 is placed inside a protective cylindrical cover 145.

FIG. 8 is a cross-sectional view of a slough 90 with a headwall 12 constructed across it showing the positions of the water (W) at one of two possible elevations (El₁) and (El₂) on a headwall 12. As the water level rises in the slough, the volume of water that is required to fill the slough increases substantially. Since the water level rises at a fairly constant rate, the flow volume and flow velocity through the tide gate increases at a non-linear rate.

FIG. 9 shows two illustrations of a SRT gate's door panel 30 mounted on a headwall 12 showing the respective water levels for the downstream water of the door panel at El₁ and EL₂ illustrated in FIG. 8. V₂ is considerably larger than V₁.

FIG. 10 is a graph showing the relative amount of water flowing through the gate opening at different times and relatively locations of the downstream water at El₁ and El₂

Operation

During operation, the forces exerted by the water flowing on the single or two door panels 30, 36 change with the rising and falling water level downstream from the SRT 10. As a result, the two door panels 30, 36 swing back and forth in the downstream body of water 99 in a 90 degree arc in response to the hydrodynamic forces exerted thereon. On a rising tide, the flow running past each door panel 30, 36 creates a drag force that acts to draw the door panels 30, 36 into a closed position. The struts 40, 45, levers and the guide lines 52, 56 oppose this force so that the door panels 30, 36 remain open. The magnitude of the force drawing the door panels 30, 36 closed gradually increases as the flow velocity and the fraction of the door panels 30, 36 submerged increases. The flow velocity increases continuously as the water level rises due to the incremental volume upstream water from the SRT gate 10 that is filled as the water level rises. In most instances, the cross section of the slough 90 is trapezoidal and the incremental volume of tidal prism filled during high water levels is significantly greater than during lower water levels. This results in the greater volume of water passing through the SRT gate 10 for a given amount of time when the water level is high compared to when the water level is low. By selectively setting the tension in the guide lines 52, 56 at the proper magnitude, the drag force will exceed the tension in the guide lines 52, 56 when the water level is at a stage that is at or very near to the desired gate closure elevation. When the SRT gate 10 begins to close, the door panels 30, 36 swing into the flow and experience an increasing drag force. The increasing drag force causes more stretching of the elastic cord 60 or the elastic cord segments. More stretching results in the single or dual door panels 30, 36 swinging farther into the flow and experiencing a larger drag force until ultimately the SRT gate 10 is completely closed. The elastic cord 60 and elastic cord sections inherently produces greater resistance as they stretch. The work (work=force×distance) done by the elastic cord 60 and cord segments also prevents the door panels from slamming shut.

As the tide continues to rise, the static head acting on the door panels 30, 36 pushes the door panels 30, 36 against the headwall 12. Eventually, the tide crests and then drops. At some point, the water levels are nearly equal on both sides of the door panels 30, 36. At this point, the tension in the guide lines 52, 56 is sufficient to counter the steadily diminishing static head. The door panels 30, 36 are then gradually pulled open by the guide lines 52, 56 connected to the elastic cord 60 and elastic cord segments. Later, when the water levels are equal, the falling tide results in water flowing out through the gate opening 20. Because the process is repeated twice daily with the tides, the upstream body of water 98 is flushed into and out of the gate opening 20 on a regular basis. Stagnation of the upstream body of water 98 behind the headwall 12 is substantially reduced.

The use of an elastic cord 60 or elastic cord segments is especially useful because the size, length and number of strands of cord or strap can be varied to define the dynamics of the guide lines 52, 56 for a given tension in the guide lines 52, 56 of the fully-opened door panels 30, 36. When the rigging tension and the elastic cord 60 are properly configured, the door panels 30, 36 will close at a controlled rate without imposing an excessive impulse on the headwall 12. If desired, when the SRT gate 10 is operating properly and the parameters of the elastic member 60 have been established, the elastic member 60 or elastic cord segments could be replaced by a more durable spring.

In the preferred embodiment, the two door panels 30 and 36 are made of steel plate or fiberglass material and each measure 72×72 inches. The elastic cord 60 or cord segment are made of bungee cord that measure 30 to 48 inches in length and stretch approximately 140% of their resting length. The bungee cord is ½ to ¾ in diameter and sheated in polypropylene or nylon. In the single door panel system, the door panel 30 measures 72×72 inches. The bungee cord is may be ⅜ to ¾ in diameter, 30 to 38 inches in length, with elongation limited to 140%. It too is sheathed in polypropylene or nylon. In the multiple elastic cord assembly 120, each cord segment is made of bungee cord that measures 30 to 48 in length and ½ to ¾ inch in diameter.

Using the above described barrier with at least one improved tidal gate, a method of preventing or eliminating the creation of stagnant water behind a barrier 12 with a gate opening is disclosed, comprising the following steps:

a. installing a headwall 12 across a slough that connects to a tideland, said headwall 12 including at least one gate opening 20;

b. installing an improved SRT gate 10 around said gate opening 20, said SRT gate 10 includes at least one door panel 32 located on the downstream side of said gate opening 20, said primary door panel 32 being pivotally mounted on one side of said gate opening 20, said door panel 32 having sufficient height and width so that when said door panel 32 is extended in a downstream direction, the gate opening 20 opens and when swung upstream, the gate opening closes, a guide line 52 attached to said door panel 32 capable of exerting a tension force on said door panel 32 to move said door panel 32 to an open position, and elastic cord 60 attached to said guide line 52 used to adjust the amount of tension force exerted by said guide line 52 needed to resist closure of said door panel 32 over said gate opening 20 caused by the flow of tidal water upstream and through said gate opening 20; and,

c. adjusting the tension of said guide line 52 so that said door panel 32 closes during high tide and gradually opens during low tide.

In compliance with the statute, the invention described herein has been described in language more or less specific as to structural features. It should be understood however, that the invention is not limited to the specific features shown, since the means and construction shown, is comprised only of the preferred embodiments for putting the invention into effect. The invention is therefore claimed in any of its forms or modifications within the legitimate and valid scope of the amended claims, appropriately interpreted in accordance with the doctrine of equivalents. 

1. A self-regulating tide gate system for regulating the flow of river and tidal waters between an upstream side and a downstream side of a main opening formed on a headwall, the tidal gate system comprising: a. at least one door panel pivotally mounted on the downstream side of said headwall and adjacent to said main opening, said door panel having sufficient height and width so that when said door panel is rotated in a downstream direction, said main opening opens and when said door panel is rotated upstream, said main opening closes b. a guide line attached to said door panel capable of exerting a tension force on said door panel to pull said door panel to an open position; and, c. an elastic member attached to said guide line, said elastic member variably adjusts the tension force exerted on said guide line so that said door panel moves to an open position when the downstream and upstream flow of water through the main opening are substantially equal, said elastic member also gradually increases the tension force exerted by said guide line to gradually resist closure of said door panel caused by the flow of water upstream and through said main opening.
 2. The self-regulating tide gate system, as recited in claim 1, wherein said elastic member is a bungee cord.
 3. The self-regulating tide gate, as recited in claim 1, further including a cable attaches to said elastic member and a winch connected to said cable that enables the force exerted by said elastic member to be selectively adjusted.
 4. The self regulating tide gate system, as recited in claim 3, wherein said elastic member is a bungee cord.
 5. The self-regulating tide gate system, as recited in claim 1, wherein said guide line affixed to said door panel and supported by a strut located adjacent to said gate opening, said strut rearward thereby enabling a rearward force to be exerted on said door panel when said guide line is under tension.
 6. The self-regulating tide gate system, as recited in claim 1, wherein said door panel is pivotally attached to a vertical pole that is rotating mounted on the said headwall adjacent to said gate opening, said vertical pole is attached to a rearward extending lever to which said guide line is attached.
 7. The self regulating tide gate system, as recited in claim 6, wherein said elastic member is a bungee cord.
 8. The self-regulating tide gate, as recited in claim 7, further including a cable that attaches to said elastic member and a winch connected to said cable that enables the force exerted by said elastic member to be selectively adjusted.
 9. The self-regulated tide gate, as recited in claim 1, further including a protective cylinder located around said elastic member.
 10. A self-regulating tide gate system for regulating the flow of river and tidal waters between an upstream side and a downstream side of a main opening, the tidal gate system comprising: a. two door panels located on the downstream side of said main opening, said door panels being pivotal mounted on the opposite sides said gate opening, said door panels having sufficient height and width so that when said door panels is rotated downstream direction said gate opening opens and when swung upstream, said gate opening closes; b. a guide line attached to each said door panel capable of exerting a pulling tension force on each said door panel to move said door panel to an open position on said gate opening; and, c. at least one elastic member attached to said guide line, said elastic member used to variably adjust and hold said door panels in an open position when the downstream and upstream flow of water through the gate opening are substantially equal and gradually increase the amount tension force exerted by said guide line needed to resist closure of said door panels over said gate opening caused by the flow of water upstream and through said gate opening.
 11. The self-regulating tide gate system, as recited in claim 10, wherein said elastic member is a bungee cord.
 12. The self-regulating tide gate, as recited in claim 10 further including a cable that attaches to said elastic member and a winch connected to said cable that enables the force exerted by said elastic member to be selectively adjusted
 13. The self-regulating tide gate system, as recited in claim 12, wherein said elastic member is a bungee cord.
 14. A method for self-regulating tide gate that includes a gate opening with at least one pivot door panel located adjacent to said gate opening that opens and closes said gate opening, said method comprises the following steps: a. attaching a guide line to said door panel; b. attaching an elastic cord so said guide line, said elastic cord being a sufficiently resilient so that said door panel may be forced open and sufficiently elastic so that said door panel may by closed; and, c. adjusting simultaneously the tension and elasticity of said elastic cord to desired amounts so that said door panel gradually opens when the force is exerted by the downstream body of water on the door panel is less than that the e force exerted on said door panel by the upstream body of water, and the elasticity of said elastic cord being adjusted so that the closure of said door panel is gradually increased by the force by the downstream body of water when it exceeds the force exerted on the door panel by the upstream body of water. 